1. Field of the Invention
The present invention relates to a light emitting display apparatus, and more particularly, to an organic light emitting display apparatus and a method of driving the same.
2. Description of the Related Art
Organic light emitting display apparatuses are display apparatuses that display an image by applying a current or a voltage to organic light emitting diodes (OLED) to emit light by electrically exciting phosphorous organic compound materials.
An OLED includes an anode layer, an organic thin layer, and a cathode layer. The organic thin layer of the OLED has a multi-layer structure including an emitting material layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) in order to improve balance between electrons and holes to increase light emitting efficiency, and may further include an electron injecting layer (EIL) and a hole injecting layer (HIL). The organic thin layer emits light when holes are combined with electrons in the emitting material layer (EML).
In general, organic light emitting display apparatuses include a plurality of pixels arranged in an N×M matrix, where N and M are natural numbers, and a plurality of driving circuits for driving each of the pixels. The pixels are driven using a passive matrix driving method or an active matrix driving method. In a passive matrix driving method, anode lines and cathode lines are arranged to cross each other perpendicularly and the lines are selected to be driven. In an active matrix driving method, a data signal is applied to each pixel using a switching device, and a capacitor is used to store the data signal, thereby maintaining a previously applied data signal during a period in which data signals are not applied. In order to realize a switching device, a thin film transistor (TFT) may be used. An active matrix driving method is classified as a voltage programming method and/or a current programming method, according to whether a voltage or a current is applied to a capacitor in order to maintain a voltage of the capacitor.
A driving transistor may be used to apply a current corresponding to a data signal to an OLED of each of the pixels. The driving transistor supplies a current according to a data signal input to a gate terminal and supplies the current to the OLED. The amplitude of the current is determined according to a difference in a gate voltage determined by the data signal and a source voltage determined by a driving voltage.
Holes and electrons are excited in the OLED by the current provided by the driving transistor, and light is emitted as the electrons and the holes are combined.